new Long Term Archive
Day-Vis image of the Chesapeake Bay (1979)
Day-IR image of the Chesapeake Bay (1979)
The Heat Capacity Mapping Mission (HCMM) was an experimental satellite program that observed thermal conditions on the Earth’s surface either during the day or at night. The mission was the first of a series of NASA Applications Explorer Missions (AEM-A). Day/night coverage over a given area occurred at intervals ranging from 12 to 36 hours with a 16-day repeat cycle.
The satellite was operational from April 1978 to September 1980. The initial orbit of 620 km was lowered to 540 km in February 1980. Coverage includes parts of the United States, Canada, Europe, Africa, and Australia. The source data were transmitted to seven ground stations and stored on binary magnetic tape. Copies of the original data were made on High Density Tapes and on black-and-white film. The HCMM source data on tape are no longer readable. Approximately 2,700 processed digital scenes were successfully recovered from a set of tapes that had been migrated to more modern media. The only full set of HCMM data that remain are on black-and-white film. The film images have been scanned on photogrammetric quality equipment, making the data available in digital format. Since the data could be of historical value for global change research, the images have been made accessible to the scientific community through EarthExplorer. The collection includes approximately 48,000 scenes that were registered to a Hotine Oblique Mercator projection.
The HCMM Radiometer operated with two channels. The first detected visible to near infrared (0.55-1.1 micrometers) radiation and the second detected thermal infrared (10.5-12.5 micrometers) radiation. The HCMM collection consists of day visible, day thermal infrared, night infrared, temperature difference, and apparent thermal inertia images. The temperature difference and apparent thermal inertia are approximations derived from radiometer measurements. More information on the conversion formulas for apparent thermal inertia can be found in the Heat Capacity Mapping Mission Anthology. HCMM nomenclature refers to the visible to near infrared channel as Vis and the thermal infrared channel as IR. The scenes are designated as Day-Vis, Day-IR, Night-IR, Temp-Diff, or Thermal-I. The spatial resolution is approximately 500 meters for the visible channel, 600 meters for the thermal channel, and 600 meters for the calculated data.
Two dataset options are available through EarthExplorer for the HCMM scenes held in the USGS EROS archive for NASA. The files are stored in TIFF format.
The HCMM Digital Source dataset includes approximately 2,700 scenes of recovered digital data with a resolution of 200 dpi based on an image that is approximately 8.5 inches wide. The scenes are 715 km wide and vary in length from 715 to 3,000 km. The file size is 3-13 MB depending on the length of the scene.
The HCMM dataset includes approximately 48,000 frames of images from film sources. The majority of the collection is day/night images that cover a 715 km x 715 km section of an original HCMM scene. This film was scanned at 1,000 dpi (25 microns) with a resulting file size of 150 MB. The elongated film containing the processed data covered a 715 km wide area on the ground but at varying lengths ranging from 715 km to 3,000 km. This film was scanned at 600 dpi (42 microns) with a file size of 70 to 150 MB depending on the length of the scene.
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please see our Data Citations and Use page at https://lta.cr.usgs.gov/citation.
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